This research project is for support of a General Clinical Research Center - Children, which encompasses a multidepartmental- multicategorical approach to clinical investigation. A variety of studies by a number of different investigators involving patients of all ages will be conducted in the Center. Individual projects which have been approved for support by the Clinical Research Center are diverse in nature. Over 40 projects are currently active and some exemplary titles are as follows: 1. Metabolic studies in children with disorders of calcium and phosphorus metabolism with or without manifest bone disease. 2. The metabolism of vitamin D3 and the therapeutic effectiveness of 25-hydroxycholecalciferol (25-HCC) in familial hypophosphatemia and vitamin D resistant rickets. 3. A study of the interrelationship of sleep phenomena and human growth hormone secretion in children. 4.The influence of human growth hormone on bile acid metabolism in man. 5. The use of conditioning with pediatric problems. 6. Evaluation of chemotherapeutic agents in malignancies, both hematopoietic and solid, in children. 7. Chromosomal abnormalities. 8. Experimental treatment of idiopathic juvenile osteoporosis. 9. Evaluation of pressor mechanisms in the mild and volume dependent hypertensions. It is anticipated that the nature of the projects supported will be continually changing as new ones are approved and others completed.